Method of separating metal from the material containing it



May 11 1926. 7 1,583,933

E. B. KIRBY Nmm OF SEPARATINGY METAL FROM THE MATERIAL CONTAINING IT Filed August 11. 1923 3 Sheets-Sheet 1 E. B. KIRBY METHODVOF'SEPARATING METAL FROM THE MATERIAL CONTAINING IT FiI Bd AI IgUSt 11. 1923 3 Sheets-Sheet 2 4/. O n e w j Q Ma /141i? 'May 11 1926. 1,583,933

5. B. KIRBY PvTIETI'HQDLOF" SEPARATING METAL FROM THE MATERIAL CONTAINING IT Filed August 11. 1925 l 3 Sheets-Sheet 5 iW- Q Q :FT I: v i i fil II 2 i 11mg- H m I r 311/ N r r PF 7* v I Patented May 11,1926- UNITED STATES EDMUND BQKIRBY, OF NEW YORK, N. Y.

METHOD OF SEPARATING METAL FROM THE MATERIAL CONTAINING IT.

' Application filed August 11, 1923. Serial No. 656,798.

, furnace product containing them, from the waste or rocky constituents of the charge.

In present practice the charge of material is fed into the top of'the blast furnace column accompanied by coke or other suitable fuel; a blast of air is injected through tuyeres near the base of the column, sometimes accompanied by injectable fuel; the furnace products such as metal, matte and slag, are drawn from the bottom of the furnace; while byproducts such as flue dust and fume are recovered from the gases which issue from the top.

My process consists of adapting the blast furnace operation, which is one of the most eflicientmethods of smelting, to the distillation of a. metal; the latter operation being at present performed in other and less eflicieut types of furnaces and at comparatively great expense.

In general the operation consists of so operating the blast furnace as to vaporize the desired metal or metals, of drawing off the gases containing the metal vapor (which gases would usually flow up to the top of the furnace through the interstices of the blast furnace column with diminishing pressure and temperature,) and of bypassingthis diverted currentof gases around the middle part of the column; subjecting them while thus temporarily separated from the column to the operation of condensation. I thus separate a comparatively volatile component of the charge not only from the slag con stituents but also from the less volatile components' It is obvious that after condensation the gases need not be returned to the column and may be rejected but I prefer to return them for the reasons hereafter explained.

My process is specially suitable for such metals as zinc, magnesium, lead, aluminum,

' but I do not restrict myself to these and the.

process-may be. applied to any metal or any chemical compound which is capable of be ing vaporized in the blast furnace by the means described hereafter.

It may in certain cases be found desirable to vaporize several metals at the same time such as'zinc and lead, and in such cases a more or less effective separation of them may be made during their condensation by having the condensing apparatus operated in successive units each of which is maintained at the temperature required to condense one of the group.

For simplicity however, I shall describe the process as if only one metal was being vaporized.

The accompanying drawings show a furnace and condensing apparatus in which my process may be operated. Since blast furnace construction and operation is well understood, I shall only indicate in the specification and drawings those features which are essential to an understanding of my improvements.

Fig. 1 is a vertical cross-section of the furnace and coke filter taken through the plane (A. A.) indicated in Fig. 2; Fig. 2is

a horizontal cross-section of the furnace and condensing apparatus through the broken plane (B.-BB indicated in Fig. 1; Fig. 3 is a vertical cross-section of the furnace and condensing apparatus through the broken plane (C.-C.CG") indicated in Fig. 2. F or, clearness conduits,valves, etc, are merely indicated without the construction details which are necessary for handling highly heated gases.

In operating my process I vaporize the metal by so arranging the charge and the operation of the furnace that the metal in question will be reduced to the metallic form before fusion and will be then subjected to atemperature which will vaporize it and that there will be a quantity of heat sufficient to convert it to vapor. I adjust and control the temperature, reducing action, and heat quantity, by the following means.

The maximum temperature attained by the material in the column is fixed by the free running temperature of the slag produced in the zone of fusion because the higher temperature of the flame in the zone of i combustion is instantly lowered by the absorption of itsheat inthe fusion of the material.

Hence, by suitably proportioning the mixtare-of ore'sand flutes I make a; slag-whose free running tem erature is above the tem perature re uire to vaporize the metal in question an r is, moreover, high enough to give the carbon and carbon monoxide a final intensity of reducing action ust before and .during fusion which will complete the reduction and prevent any important residue of the metalfrom combining with silica as oxide and entering ths slag.

In the case of very ch material, such as scrap refuse or bar metal 'to be .re-distilled for purification, there is but little slag and.

the temperature attained is fixed by the boiling point of the metal.

The total extent of reducing action to which the -material is subjected is governed not only by the maximum tem erature created at the zone of fusion, but a soby the relations between size and permeability of the lumps of material and the length of time occupied by their descent, the latter being controlled-mainly by the speed of the furnace and the height, cross-section and shape of the column.

In the usual operation of a blast furnace, the quantity of heat liberated by combustion is that required to fuse the metal, slag and other products, to perform the chemical reactions upon the material and to make up the various losses.

In my process I sup ly not onl the above normal requirements ut also a arge additional uantity of heat equal to the latent heat 0 vaporization plus the extra losses incurred in the condensation circuit. I do this by using an adequate excess of fuel and blast above the roportions required by the material for or inaryblast furnace reduction and fusion.' By the various means thus indicated; I so roportion the blast furnace and so. adjust its operation that the metal I wish to vaporize will practically all. be converted to gaseous v throughout the interstices of the column to the top where they leave thefurnace. During their ascent their pressure and temperadecrease and their. composideredv by the excessive volume of the gases.

- purpose of vapor.

In ordinary blast furnace operation the products of combustion rise ture graduall tion is modi ed by various reactions with -the components of the column. 'If the smelting is so conducted as to variorizethe desired metal and the furnace gasesare drawn out of this column for the condensing the metallic vapor contents the latter operation will be hin- The metal-vapor constitutes such a small proportion of the total volume that its low. partial pressure lowers the condensationpoint to an extent which destroys the conditions required for condensationto liquid metal. Cooling below-a certain-limit; yields a. product winch is in solid .particle ;mued

with more or less oxide in case certain gases are present to react with it: the blue powder produced in the condensation of zinc being a familiar instance. I

The first requirement therefore is to obtain a gas which is rich enough for. condensation. I do this by using a blast'composed of pure oxygen or of -air sufficiently enriched with oxy en. This reduces the volume of the gases y eliminatingthe nitroen wholly or nearly so and'by saving the uel consumed tov heat this'nitrog'en. The reduction of volume of the gases pro rportionally raises the percentage of t eir metallic vapor content.

It is also necessary to provide for the reduced percentage of vapor towards the end of the condensing operation for this, if not separated in some form (such as bluepowder for zinc? will be carried to waste by the large vo ume of gases. I do it by returning the current to the blast furnace column in the cooler portions of which this residue of vapor will be, precipitated as metal or oxide or otherwise and this 'precipitate will be carried down by the column back to the zone of fusion.

Any'precipitated fume too -im alpable to be retained by the column wi pass-out 'of the furnace top with the gases and may be caught in baghousesor other ,well known means for. collecting such fumes from blast "furnace gases. I therefore operate the con denser at tem eratures which are aboye the limit at wh-ic solid precipitate begins to form, but which are low enough to condense liquid metal.

I also raise the (percentage of metal vapor another expe ient which ma be emb ployed either with or without t e use of oxygen in the blast.

This is to pass through the condensing apparatus only a portion of the total gases formed; the remainder bein ,allowed to rise through the interstices of t e column. As

the coolerregions are reached the metal vapor isforms while the gases'escape from of the furnace.

The-precipitate is carried back b precipitated as metal or in other the one portion which is returned ith ut conthe top .descend'ing column to the zone of usion densation and another portion which is conpoint where densed.

Another method will be to pass all the gases through the condensing apparatus and to so operate this apparatus as to leave a suflicient residue of uncondensed vapor in the current which re-enters the column.

Such equivalent methods may be preferable in order to meet special conditions such as a clogging of the interstices of the middle part of the column, and I- do not restrict myself as to their choice.

In treating the current of gases drawn from the furnace column I do not restrict myself to any particular apparatus or method for performing the condensation of the metallic vapor. The current may be rejected after condensation or it may be returned to the column at a higher level in order to return its residual metal vapor contents and its heat contents to the column.

Nevertheless, the capacity of blast furnace operation so greatly exceeds that of any present furnaces used for distillation .processes that the condensation required will be on a scale never before attempted. Present apparatus and methods are not suitable for the Work and I have therefore invented improvements in condensation which will meet the new conditions which are briefly outlined as follows.

The daily tonnage of metal to be con densed is so great that the quantity of latent heat to be absorbed from the condenser requires definite and accurately controlled cooling apparatus and methods instead of those now employed.

Moreover, nace at the point of maximum vapor content, which will be near the zone of'fusion, have a high temperature (1100 to 1300 C. in the case of zinc) and unless much of this visible heat is returned to the furnace in some way more fuel will be required to do the furnace work and this aside from its cost will increase the volume of furnace gases.

Again blast furnace gases, unlike those of distillation furnaces, contain much carbon dioxide, steam and free oxygen at the they are drawn oil". and they will also carry dust and fume which would soon clog the condensing apparatus. The carbon. dioxide steam and oxygen oxidize the metal during condensation and must therefore be reduced to safelimits. In order to pass the current through the interstices of a large mass of lumps of coke or other carbon fuel, maintained at a temperature as near as possible to the furnace maximum. This hot carbon filter eliminates the carbon dioxide, steam and free oxygen; reduces and vaporizes any oxide fume and catches the ust:

ture for liquid the gases drawn from-the fur-v meet these requirements I first I then remove the visible heat until the current has the most effective temperature for condensing the metal in question which in the case of zinc will usually be the range between 600 and 800 C. I prefer to return the heat removed column by means of a pair of regenerators.

Having thus reached the proper temperacondensation, the current enters the condenser proper where the latent heat is removed by an artificial cooling of the walls through the flow of a cooling medium which is under positive and accurate regulation.

Referring. to the accompanying drawing in which is shown apparatus suitable for carrying out my process: the blast'furnace column, with the charge and the fuel usually in alternate layers, is indicated at (1-1) and the blast tuyeres at (2). The tapping arrangements for metal and slag are merely indicated. A column (334) of coke or other form of carbon fuel is arranged in any convenient way so as to join the main column at (5) just above the zone of fusion. The lower part '(3-3) of this coke column constitutes the hot carbon-filter, the upper or cold portion (4) constituting merely a gas tight bin to suppl the filter.

The contact (5-6) between the columns is an inclined surface owing to the fact that the charge is heavier than the coke. This fluctuating surface, dragging away some: of the coke, maintains way whereby the gases may escape from the furnace column into the more open and free interstices of the coke column. They leave the carbon filter at (7) to pass to the condensing apparatus.

The slagged dust accumulations and cdke ash flows down the sloping conduit into the main column. The coke is consumed slowlv and fresh coke the cold upper part of the column which is replenished occasionally by any suitable gas tigljt )feeding apparatus such as is indicated at 8 The current passing through conduit (79) enters the condensing apparatus through a regulated damper or throttle indicated at (10) which is constructed of any suitable refractory material. This admits to the condensing apparatus such a fraction of the total furnace gases as is desired.

The condensin a aratus consists of two a large open passageis supplied by gravity front llO temperature of the furnace (l100--1300 smelti g z nc). A s t... s' ds through the conduit (15) and rises through the passages of regenerator (16 it deposits enough heat in them tofbe re uced to the temperature at which condensation can begin (800 C. for zinc). It then flows down the parallel passages (18-18) of the condenser where latent heat is removed through the cooled walls'(33)- andliquid metal is condensed.

Since the percentage of metal vapor be comes less, as theogeration proceeds the temperature must be 'owered to correspond so that the extremity of the condenser at (19) is kept cooler than the topwhere fresh. gas is enterlng.

At (19) the cool end of the condenser, the current, with what-remains of uncondensed residual vapor, is down to the minimum temperature .allowed (say about 600 C. in the case of zinc).- Before returning to the furnace column its visible heat is restored by passing it backwards throughthe other condenser (20-20), regenerator (22) and regenerator conduit (23) which are full of heat stored during the previous reversal of current. The current therefore emerges from the regenerator conduit (23) restored to its original temperature (losses disregarded) and passes to the furnace column by conduits (24-25- -26'27) and the furnace wall enlargements (28-28). The latter are pro- I ,vided in order to give the gases free access to a, large open inclined surface of the column sothat they may freely enter its interstices.

Reversing valves i dicated at (11-12-- 13-14) periodically reverse the current through the denser sets (16-18) and (2220). The regenerators may be of any of the forms known in metallurgical practice... They are chambers filled with fixed brick work ortile or with loose stone or bricks or other suitable material capable of absorbing and storing heat. The form I prefer has the open d'own' conduit (15') and the tile filled vertical chamber (16) which receives the current from its lower end (31). There is' a sump and tap hole (32) at the bottom for collecting and removing slagdrip. i

The condensers may like regenerators, many forms are lmown 1n the art.- I prefer agroup of vertical narrow condensing conduits (two shown in draw ing) set inparallel and illustrated by (18- 18).- Each conduit has a large amount of wall surface which is cooled by a regulated current of waterzor air ortother'suitable medium fiowing-on the other side of the wall.

Those shown have a lining-of refractory-.material (33) of thickness suitable for transmitting the r uired flow of latent'heat and this is absorbe ,by a metal jacket (34) with regulating means for the-flow ofwater or air, etc. through it at a suficientrate. to

duplicate regenerator and con-- beof any design, for

' may be filled with lumps of coke, rock, tile or other material to diffuse the current and absorb heat. A receptacle (35) and an inverted siphon tap (36) serve to collect and remove the condensed metal.

\Vhen a plurality of metals is vaporized, for instance zinc and lead, the condenser of each set and preferably both regenerator and condenser will be made in two units following each other.

In the first unit the-condenser would be maintained below 1525 C. the condensing point for pure lead vapor and above 930 C. the condensing point for pure zinc vapor (effect of blast pressure disregarded). The current after the condensation of its lead vapor would pass to the second unit where at the lower temperature required the zinc would be condensed.

Many forms of reversing valves for high temperature gases, arranged and operated in: many ways, are known in the art in connection with regenerative work and I do not restrict myself to any particular design or method for use in my process. I have therefore merely indicated at (1112-13-14) the valves required to reverse the current.

Y It is an important and novel feature of my system that I operate my condenser hot enough to condense liquid metal only and then precipitate all the uncondensed resid ualvapor in the interstices of the blast furnace column. I

the problem in hand by raising or lowering the point 28 ofre-entry.

' ,I do not iestri'ct myselfto this method-ofxnoving thecurrent which may obviously be'move'd by other means such as a blower placed at the coolest endof the'condenser.

In employing one enrich m ..a blast off pure oxygen or oxygen, I protect the tuyere fan or thus return to the furnace I promptly and efiiciently all metal which 135- nozzles, not only by the usual water cooling,

but by injecting a little steam in such a wavas to act upon the incandescent coke which adjoins or. radiates upon them, an

enough to properly slow up and cool the current and thus to precipitate its residual vapor contents. I

The vaporization of the metal in question does not interfere with the fusion and separation of the liquid metals, matte, slag, etc. in the usual way, nor with the usual collection of flue dust and fume from the waste gases leaving the furnace.

Having described my invention, I claim 1. The method of separating a metal from I the material containing it which consists in smelting the material in a blast furnace with such excess of fuel. as will supply latent heat of vaporization to the metal, in making a slag whose free running temperature exceeds the boiling point of the metal, in subjectingthe material to reducing agents for a time suflicient to reduce the metal before fusion, in drawing off the gases and condensing the metal vapor, in returning the gases to the furnace column at an elevation hi her than that at which they are drawn ofl in enriching the gases by causing an accumulated portion of the metal to traverse a closed circuit which includes part of the column, and in maintaining the condenser temperature above the point at which solid precipitate is formed and precipitating the residual vapor within the interstices of the column.

2. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace with such excessof fuel as will supply latent heat of vaporization to the metal, in making a' slag whose free running temperature ex ceeds the boiling point of the metal, in subjecting the material to reducing agents for a time sufficient to reduce the metal before fusion, in drawing off the'g-ases and condensing the metal vapor, in returning the gases to the furnace column'at an elevation higher than that at which they are drawn off, in enriching the gases by causing an accumulated portion of the metal to traverse a closed circuit which includes part of the column, and in withdrawing the latent heat of condensation through the condenser walls to a cooling medium of accurately regulated flow.

3. The method of separating a metal from the material containing'it which consists in .tent exceeds that of air,

smelting the material in a blast furnace with such excess of fuel as will supply latent heat of vaporization to the metal, in making a slag whose free running temperature excceds'the boiling point of the metal, in subs jecting the material to reducing agents for a time suificientto reduce the metal before fusion, in drawing off the gases and condensing the metal vapor, in returning the gases to the furnace column at an elevation higher than that at which they are drawn off, in enriching the gases by'causing an acumulat ed portion of the metal to traverse a closed circuit which includes part of the column, and in returning visible heat from the gases to the column by reversing flow through regenerators.

4. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace with such excess of fuel as will supply latent heat of vaporization to the metal, in making a slag whose free running temperature exceeds the boiling point of the metal,

in subjecting the material to reducing agents for a time sufficient to reduce the metal before fusion, in draw ng off the gases and condensing the metal vapor in returning the off, in enriching the gases by causing an accumulated portion of the metal totraverse a closed circuit which includes'part of the column, and in'passing the gases through a highly heated carbon filter. I

5. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace with such excess of fuel as will supply latent heat' of vaporization to the metal, in making a slag whose free running temperature ex- I ceeds the boiling point of the metal, in subjecting the material to reducing agents for atime sufficient to reduce the metal before fusion, in using a blastwhose oxygen conin drawing off the gases and condensing the 'metal vapor, in returning'the gases to the furnace column at an elevation igher than that at which they are drawn off, and in maintaining the condenser temperature above .the point at which solid precipitate is formed and precipitating the residual vapor within the interstices of the column.

6. The method of separating a metal from the material containing it which consists in smelting the material in 'a blast furnace with such excess of fuel as will supply latent heat of vaporization to the metal, in making a slag whose free running temperature exand condensing the metal vapor, in returning the gasesto the furnace column at an elevation higher than that at which they are drawn off, and in withdrawing the latent heat of condensation through the condenser walls to a cooling medium of accurately regulatedflow.

7 The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace with such excess of fuel as will supply latent the gases :by causing an accumulated portion i of vaporizatlon to slag whose i the gases to thecolumn by reversing flow.

subjecting for a timesuflicient t'ovreduce the metal before fusion, in using a blast whose oxygen heat of vaporization to the metal, in making a slag whose free running temperature exceeds the boiling point of the metal, in subjecting the material to reducing agents for a time sufficient to reduce the metal before fusion, in using a blast whose oxygen content'exceeds that of air,

in drawing OR the gases andcondensing the metal vapor, in

.returning the gases to the furnace column at an elevation higher than that at which they are drawn off, and in passing the gases through a highly heated'carbon filter.

8. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace with such excess of fuel as will supply latent heat oflvaporization to the metal, in

making a slag whose free running temperature exceeds the boiling point of the metal, in the material to reducing agents content exceeds that of air, in drawing off the gases and condensing the metal vapor, in returning the gases to the furnace column at an elevation hi her than that at which they are drawn 0 ,and in enriching of. the metal to which includes part of the column.

9. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace with such excess of fuel as will supply latent heat the metal, in making a free running temperature exceeds the boiling point of the metal, in subjecting the material to reducmg agents for a time suflicient to reduce the metal before fusion, in usin ablast whose oxygen content exceeds at of vair, in drawing off the gases and condensing the metal vapor, in returning the-gases .to the furnace column at'an elevation higher than that at which they are drawn off, and inreturning visible heat from traverse a closed circuit "through regenerators.

i 10, The method of separating a metal from the material containing :1t which consists in smelting the material in a blast furnace with such excess of fuel as will supply latent'heat of vaporization tothe metal, in ,ma king a slag whose free running temperature exceeds the boiling point of the metal, in subjecting a time sufficient in using a blast whose oxygen content exceeds that of air, in drawing off the gases and condensingthe metal vapor, in returning the gases to the furnace column at an eleva 'tion higher than. that at which they are drawn off, in enriching the gases by causing an accumulated traverse a closed circuit which includes part of the column, in passing the gases through a highly heated carbon filter, 1n withdrawing the latent heat of condensation through the condenser walls to a cooling medium of accurately re ulated flow, and in maintainin the con enser temperature above the po1nt at which solid precipitate is formed and precipitating the residual vapor within the interstices of the column. 11. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace with such excess of fuel as will supply latent heat of vaporization to the metal, in making a s a the boiling point of the metal, in subjecting the material to reducing agents for a time suflicient to reduce the metal before fusion, in using a blast whose oxy en content exceeds that of air, andin drawing off the gases and condensing the metal vapor.

12; The method of separating ametal from the material containing it whlch consists in smelting the material in a blast furnace with such excess of fuel as will supply latent heat 0 whose free running temperature exceedsportion of the metal to slag hose free running temperature exceeds the boiling point of the metaL'in subjecti'ng the material ,to' reducing agents for to reduce the metal before fusion, in using'a blast whose oxygen content exceeds thatof air, in drawing off-the ases and condensing the metal vapor, and' m enriching the gases by causing an accumulated portion of the metal to traverse a closed circuit'within the column.

13. The method of separating a metal from the materialcontaining it whlch consists in smelting the material in a blastfurnace and creating conditions which] vaporize the 1 metal, indrawing off the gases and condensing the metal va or, in returning thegases to the furnace co umn at an elevation hlgher than that at which they aredrawn off, and in assin the gases through a highly heated car on F1 ter.

14. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace and creating conditions which vaporize the metal, in drawing off the gases and condensing the metal vapor, in returning the ases to the furnace. column at an elevation higher than that a twhich they are drawn off, and in passing the gases through-a highly'heated smeltingthe material in a blast-furnace, and

regulated flow.

creating conditions which vaporize the metal, in drawing off the gases and condensing the metal vapor, in returning the gases to the furnace column at an elevation higher than ,that at which they are drawn off, and in maintaining the condenser temperature above the point at which solid precipitate is formed and precipitating the residual vapor within the interstices of the column.

' 17. The method of separating a metal from the material containing it which consists in smelting the material in a blast furnace and creating conditions which vaporize the metal, in using a blast Whose oxygen content ex ceeds that of air, in drawing off the gases and condensing the metal vapor, and in returning the gases to the furnace column at an elevation higher than that at which they are drawn off.

18. The method of separating a metalelevation higher than that at which they are.

drawn oil', and in enriching the gases by causing an accumulated portion of the metal to traverse a closed circuit which includes part of the column.

19. The method of separating a metal from the material containing it which consists in smelting the material in ,a blast furnace and creating conditions which vaporize the metal, in drawing off the gases and condensing the metal vapor, in returning the gases to the furnace column at an elevation higher than that at which they are drawn off, and in withdrawing the-latent heat of condensation through the condenser walls to a cooling medium of accurately 20. The method of separating 'a metal from the material containing it which conoff, and in returning visible heat from the I gases to the column by passing them through regenerators. 7

21. The 'method of separating a metal from the material containing it which consists in smelting the material in a blast furnace and creating conditions which vaporize the metal, with a' blast whose oxygen content exceeds that of air, in so injecting steam as to react with the adjacent fuel and protect the tuyere nozzles, and in drawing off the gases and condensing the metal vapor.

22. The method 'of separating a metal from the material containing it which consists in smelting the material in a blast furnace and creating conditions which vaporize the metal, with a blast whose oxygen content exceeds that of air, in so injecting steam as to react with the adjacent fuel and protect the tuyere nozzles, in drawing off the gases and condensing the metal vapor, and in returning the gases to the furnace column at an elevation higher than that at which they, are drawn ofi.

23. The method of separating metal from the material containing it which consists in vaporizing the metal in a furnace in a cur rent of othergases, in drawing ofi' the'gases from the point of maximum richness and condensing-the metal vapor, and in returning the gases'to the furnace for the recovery of their residual vapor contents and heat.

24. The method of separating a -metal from the material containing it which consists in vaporizing the metal in a furnace in a current of other gases, in drawing off the gases from the point of maximum richness and condensing the metal vapor, in returning the gases to the furnace for the recovery of theirresidual vapor contents and heat, and in enriching the gases by causing an accumulated portion of the metal to traverse a closed circuit.

25. The method of separating a metal from the material containing it which consists in vaporizing the metal in a furnace in a current of other gases, in drawing 011' the gases from the point of maximum richness and condensing the metal vapor, 'in returning the gases to the furnace for the recovery of their residual vapor contents and heat, in passing the gases through a highly heated carbon filter, and in returning visible heat from the gases to the column by passing them through regcnerators.

26; The method of separating a plurality of metals from the material containing them which consists in vaporizing the metals in a current of other gases, in drawing off the current and condensingthe metals, by passing it through a condenser of several sections each maintained at the temperature of condensation for-one of said metals, and in returning the gases to the furnace for the recovery of their residual vapor contents. 7

The method of separating a metal from the material containing it which consists' in vaporizing the metal in a furnace in a current of other gases, in drawing ofithe'gas'es and condensing the metal vapor, and in passing; the current successively through a regenerator and 'a condenser then backwards through another condenser and regenerator and nto the furnace, the currentbeing reversed periodically between the two sets ofregenerators and condensers.

28. The method of separating a metal from the material containing it which consists in vaporizing the metal in a furnace m a current of other gases, in drawing of! the gases and condenslng the metal vapor,

by passing the current through a highly heated carbon filter,-then with periodic reversals through twosets-of regenerators and condensers, which sets are connected at the coolest ends of their respective condensers, and then 'back to the furnace.

In testimony whereof, I hereunto aflix my signature; t

B. KIRBY. 

